When a circuit board operates abnormally, an automatic optical inspection (AOI) device is used to find a corresponding defect of the circuit board.
Referring to FIG. 10, this is an isometric view of a typical AOI device. The AOI device 90 includes an entrance unit 92, an inspecting unit 94, a defective product unit 96, and a non-defective product unit 98. The entrance unit 92 is connected to the inspecting unit 94, and is used to provide circuit boards that need testing to the inspecting unit 94. The inspecting unit 94 is used to test the circuit boards, and then sends defective circuit boards and non-defective circuit boards to the defective product unit 96 and the non-defective product unit 98 respectively. The defective product unit 96 and the non-defective product unit 98 are mechanically and operatively connected to the inspecting unit 94.
The inspecting unit 94 includes a slide way 941, a slide block 942, an image pick-up device (not shown), and a light source 943. The slide way 941 is a metal transmission band, and is used to transmit the circuit boards needing testing from the entrance unit 92 to a testing position in the inspecting unit 94. The slide block 942 has a carrier tray attached thereto. The slide block 942 moves along the slide way 941 and thus carries the circuit boards to various locations in the inspecting unit 94. The light source 943 illuminates the circuit boards. The image pick-up device is adjacent to the light source 943, and photographs the circuit boards to obtain images.
Referring to FIG. 11 and FIG. 12, these respectively show images of a standard circuit board without defects, and a corresponding defective circuit board. A typical method for testing the defective circuit board using the AOI device 90 includes the following steps. First, a circuit board which works normally as a standard circuit board is transmitted from the entrance unit 92 to the inspecting unit 94. Second, once the standard circuit board has arrived at a position below the light source 902 and the image pick-up device, the standard circuit board is illuminated using the light source 902. Thereby, a standard image (as shown in FIG. 11) using the image pick-up device is obtained. Third, a circuit board needing testing is provided, and the above steps are repeated to obtain a diagnostic image. Fourth, the image pick-up device compares the diagnostic image with the standard image in order to determine whether the circuit board under test is defective. Fifth, the circuit board under test is delivered to the defective product unit 96 or the non-defective product unit 98 by the slide way 941 according to the result of the determination. For example, when a region of the diagnostic image is different from the corresponding region of the standard image, the circuit board under test is regarded as a defective circuit board. Such kind of region is designated as “A” in FIG. 12. Thus the defective circuit board is transmitted to the defective product unit 96 according to the result of the determination.
However, in general, the AOI device 90 can only be used to detect metal lines of a circuit board. The AOI device 90 cannot be used to detect active components or other passive components of a circuit board. That is, the AOI device 90 cannot test all the elements of a circuit board in the testing process.
What is needed, therefore, is a circuitry testing device and a circuitry testing method that can overcome the above-described deficiencies.